1. Field of the Invention
The present invention relates to novel and unique methods for manufacturing super-micro fibers. More specifically, this invention relates to methods for manufacturing super-micro fibers using single-path and twin-screw extrusion processes to produce super-micro fibers having dimensions between 0.003-0.0003 denier per filament.
2. Description of the Prior Art
Super-micro fibers are very thin fibers with silk-like properties. Although thinner than silk, super-micro fibers are much more durable, less brittle and less sensitive to environmental factors such as corrosion and moisture, etc. Super-micro fibers are used in the fashion industry to produce sportswear and other forms of attires. These fibers have also been used in the electronic industry and other industrial applications seeking to avoid the wear and tear associated with the use and application of conventional fibers.
Super-micro fibers are manufactured by combining, blending and extruding two or more polymers. The final products are obtained by separating the wanted polymer(s) (the super-micro fibers) from the unwanted polymer(s) using a solvent. As starting materials, the polymers generally used are polyesters, copolyesters, polyamides and copolyamides.
Examples of polyesters, copolyesters, polyamides and copolyamides used as starting materials for producing super-micro fibers are disclosed in U.S. Pat. No. 5,555,716, which teaches that polyamides and copolyamides are well known by the general term “nylon” and are long-chain synthetic polymers containing amide (—CO—NH—) linkages along the main polymer chain. That typical polyamides include nylon 6, nylon 6/6, nylon 6/10, nylon 6/12, nylon 6T, nylon 11, nylon 12, and copolymers or mixtures thereof. That polyamides can also be copolymers of nylon 6 or nylon 6/6 and a nylon salt obtained by reacting a dicarboxylic acid component such as terephthalic acid, adipic acid, or sebacic acid with a diamine such as hexamethylene diamine. U.S. Pat. No. 5,555,716 further disclosed that suitable polyesters and copolyesters include, for example, those prepared by the condensation of aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid and naphthalene-2, 6-carboxylic acid, and aliphatic dicarboxylic acids such as adipic acid or their esters with diol compounds such as ethylene glycol and diethylene glycol; and that preferred polyesters include polyethylene terephthalate and polybutylene terephthalate.
Because manufacturing of super-micro fibers is highly specialized, the types of manufacturing processes used are sure to influence the overall cost of production and, more importantly, the desired dimensions of the super-micro fiber products. In Patent Nos. 177413 and 168750, Republic of China, there are disclosed processes for manufacturing super-micro fibers which used polyesters and polyamides as starting materials. The processes utilized a special spinneret plate design to spin the polyamide-polyester complex. The complex was melted and one polymer was removed to produce the micro fibers. However, such processes are limited by the spinneret plate design. A single orifice of such a design arrangement can only have 37 partings, which result in the production of micro fibers with filament dimensions of around 0.025 denier.
Japan Patent Publication Nos. 40-9429, 41-7886, 41-7893 and 51-6261 disclosed processes for manufacturing super-micro fibers. These patents collectively disclosed blending polyamide or polyester with polyethylene (PE), polypropylene (PP), or polystyrene (PS) granules. The blended mixture is spun, the continuous phase is melted and removed by solvents to obtain the super-micro fibers. These prior art processes used solvents such as xylene and toluene to dissolve the PE, the PP or the PS component (the continuous, sea-phase component) from the polyamide component (the stationary, island-phase component). A major draw-back is that solvents like xylene and toluene used in the prior art processes are known to cause serious damage to the environment, are hazardous to humans and other life forms and are relatively expensive as compared to other commercial solvents.
Other prior art processes are known to use polyamide with polyethylene terephthalate as starting materials for producing super-micro fibers. These processes do not teach adding an affinity mixture to the polyamide-polyethylene terephthalate mixture to increase affinity between the polyamide and the polyethylene terephthalate mixture components prior to blending and during blending of the polyamide-polyethylene terephthalate mixture; nor do they teach the addition of an affinity mixture which constitute a predetermined weight percent of the total reaction mixture needed to produce super-micro fiber products having dimensions between 0.003-0.0003 denier per filament. Thus these prior art processes which used polyamide and polyethylene terephthalate as starting materials were known to have encountered difficulties with their respective blending and spinning reaction process steps.
As an example, Japan Patent Publication No. 8-27626 disclosed a method for producing super-micro fibers that combines polyamide and polyethylene terephthalate, which is then spun at high temperature for quite a long time to produce the desired super-micro fibers primarily containing polyamide. Because this prior art process does not add an affinity mixture processing requires blending and spinning at a high temperature for a considerable length of time to increase the affinity between the polyamide and the polyethylene terephthalate ingredients. But in practice the processing time for blending and spinning is not long enough to enhance affinity prior to pyrolosis. That is, continuous blending and spinning at high temperature result in severe pyrolosis of the mixture's ingredients thereby affecting the spinning characteristics of the micro fibers and diminishing the quality of the yarn produced.
Prior to this present invention none of the existing prior art, individually or collectively, had disclosed methods for producing super-micro fibers comprising the following steps: blending polyamide-polyester mixtures having specific concentration ratios; adding an affinity mixture to increase affinity between ingredients within the polyamide-polyester mixtures; using single-path and twin-screw extrusion processes for extruding the polyamide-polyester mixtures; spinning and drawing the polyamide-polyester mixtures; and dissolving the polyester-mixture components from the polyamide mixture components to obtain the polyamide, super-micro fiber components having dimensions between 0.003-0.0003 denier per filament.
Accordingly, it is an object of this invention to disclose methods for manufacturing super-micro fibers which add an affinity mixture to their polyamide-polyester solution mixtures to increase affinity between the polyamide ingredients and their polyester ingredients prior to blending, during blending and during spinning of their solution mixtures.
Another object of this invention is to disclose methods for manufacturing super-micro fibers capable of reducing overall manufacturing cost with the use of single-path and twin-screw extrusion processes, capable of manufacturing at temperatures much lower than manufacturing temperatures of the prior art, and capable of producing thinner super-micro fibers having dimensions between 0.003-0.0003 denier per filament.
It is a further object of this invention to disclose methods for manufacturing super-micro fibers which use less toxic solvents such as alkaline base solvents to dissolve the sea-phase polyester components from their polyamide-polyester mixtures to form the island-phase, polyamide components or super-micro fiber products.
Still, it is a further object of this invention to disclose methods for manufacturing super-micro fibers which use solution ingredients having precise weight percent based on the weight of their respective solution mixtures, and precise ranges of melting viscosity ratios, addition ratios, spinneret packed pressures, minimum intrinsic viscosities and take-up velocities to form steady island-phase polyamides or super-micro fiber structures.